As a cutting insert attached to the above-described removable insert-type cutting tool for milling machining and to a removable insert-type cutting tool to which the cutting insert is attached, there are known, for example, those described in Patent Document 1, in the cutting insert and the removable insert-type cutting tool described in Patent Document 1, a chip removing flute is formed on an outer circumference of a cylindrical tool main body which rotates axially. Furthermore, on an outer circumference of the tool main body, there are formed a plurality of insert seats opened on a wall surface of the chip removing flute facing forward in the rotating direction of the tool main body. The cutting insert is attached to each of the insert seats.
In this instance, the above-described cutting insert is a flat plate formed approximately in a regular triangle shape, with one of the regular triangle surfaces thereof facing outside in the radial direction of the tool main body. Furthermore, the opposite regular triangle surface is closely attached to the bottom surface of the insert seat facing outside in the radial direction of the tool main body. One of the three side surfaces around the regular triangle surface faces forward as a rake face in the rotating direction of the tool main body. The remaining two side surfaces are closely attached respectively to a pair of wall surfaces of the insert seat formed in a recessed V-shape.
As described above, in the removable insert-type cutting tool to which the cutting insert is attached, on cutting a workpiece, the tool main body is rotated around the axis line and also fed out in a direction intersecting with the axis line. Thereby, a cutting edge formed at a ridge part between regular triangle surfaces positioned outside in the radial direction of the tool main body is used to out the workpiece on the rake face of the cutting insert, thus forming a machined surface on the workpiece.